ABSTRACT
Autoimmune and paraneoplastic disorders can produce findings suggestive of viral illness. Autoimmune encephalitis may present similarly to viral encephalitis, psychiatric disorders, or epilepsy. Specific autoantibodies to important brain proteins, such as the NMDAR, define treatable forms autoimmune encephalitis. Paraneoplastic cerebellar degeneration may enter into the differential diagnosis of viral cerebellitis but has important cancer associations, and different prognosis, and different responses to treatment. Other autoimmune disorders such as ADEM, neurosarcoidosis, CNS lupus, Neuro Behcet disease, and CNS vasculitic may enter into the differential diagnosis of CNS infections. The conventional paraneoplastic syndromes and the CNS synaptic autoantibody disorders are associated with a risk of specific tumors. Diagnosis of these disorders requires careful examination, evaluation of CNS imaging, and often autoantibody testing. Treatment should be directed based upon the underlying autoimmune mechanisms.
